Been doing that for years now. I have a end line post di manual shutoff valve and the standard flush valve at the restrictor. Upside of working with a long time pro who sets up rodi and soft water systems as a side hustle, got taught well, lol.Are you doing an After Flush by opening the Valve that came with your RO? Also you need to do a Start Flush by adding a Valve after the Clean Side of your RO, Flush from that point for about a minute, close and Slowly open your Final Valve to keep your DI Canisters full of Water. Chloramine just loves air to activate.